United States Unpaved Roads Tagging
There is conflicting information on this topic at several places. Please see Talk:Highway tag usage and the Talk-US Mailing List for discussion.
Overview
There are a lot of conflicting techniques for tagging unpaved roads in the United States. In the Mid and Mountain West states of the USA, the proportion of Unpaved to Paved roads gets very high, for example in Colorado, approximately 70% of all roads in the states are unpaved, and these roads are used for 'daily driving' as much as paved roads. As such, the importance of the use of high quality unpaved roads in routing is high. Dependence on paved roads for routes can add enormous times and distances for cross-country travel. Conversely, there are many unpaved roads that cannot be safely traveled in a Sedan, the base transportation level for routing software.
Where this guide conflicts with other pages
In general, the emphasis on other pages has been to tag all roads that do not have a paved surface as tracks. This page directly contradicts that statement. The emphasis is on the functionality and purpose of the road, rather than the quality of the road surface.
Unpaved Roads vs. Dirt Roads
The subject can be broken down into 2 broad groups, Unpaved Roads and Dirt Roads. Both types can have State or County designation. Here is a comparison table
| Description | Unpaved | Dirt | Discussion |
|---|---|---|---|
| Other Names | Graded Road, Gravel Road | Jeep Trail | Most unpaved highways in the Mid-West are graded, that is they are levelled and widened using locally extracted and crushed rock, and the surface then smoothed with a grader. Routine maintenance involves cutting off the top layer to eliminate the washboarding effect. Jeep trails, if there is any maintenance at all, tend to be repaired using materials available in-situ. There may be no requirement for local authorities to maintain Jeep trails, and are sometimes repaired by volunteer organizations associated with off-roading |
| Number of Lanes | From narrow 2 to wide 2 | 1, with passing places | |
| Speeds | Speeds up to and above legal maximum are often obtained | Speed tends to be below 20 mph | |
| Routing | Software should use route at almost same priority as paved route | Software should ignore road for routing purposes |
Identifying the road type from Imagery
Generally, distinguishing the two types is easy. Unpaved roads look similar to paved roads in their construction, but appear paler in the image. Dirt roads tend to have 2 distinct tracks, where wheels have cut through the groundcover. Their appearance is described in tracktype=*
Tagging Comparisons
| Tag | Unpaved Road | Dirt Road | Associated Tag |
|---|---|---|---|
| Surface | Unpaved,Gravel | Dirt | surface=* |
| Tracktype | Always grade1 | Appropriate tag | tracktype=* |
| Lanes | 2 | 1 | lanes=* |
| Smoothness | bad | Appropriate Tag | smoothness=* |
| 4wd_only | no | maybe | 4wd_only=* |
Seasonal Access
Roads may be closed seasonally, especially in mountain areas, use access=* with the conditional option, e.g. access:conditional=no @ winter to improve usability of the information
Tiger Data
Naming errors in Tiger imports
Bulk imports of Tiger data consistently produce the following errors.
| Tiger Name | Actual Name | Ref |
|---|---|---|
| Road North | County Road N | CR N |
| Road West | County Road W | CR W |
| Road South | County Road S | CR S |
| Road East | County Road E | CR E |
| Road Railroad | County Road RR | CR RR |
Abbreviations For Ref Tags
| Description | Name | Ref |
|---|---|---|
| Roads with county designation | County Road N | CR N |
| Roads with US Forest Service designation | Forest Road 123 | FS 123 |
| Roads with Bureau Of Indian Affairs Designation | Indian Route 456 | IRR 456 |
To tag routes with multiple designations, separate ref with semi-colon: CR N;FS 123;IRR 456
Fixing Tiger Data
This example shows imagery of the intersection of 2 county roads in Baca County, Colorado. Both roads are tagged by tiger as residential. Based on the above criteria, The East-West route (County Road Q) should be changed to unclassified, the North-South route (County Road 21 5/10) should be changed to a track.
Mineral Exploitation Roads
Tracks serving Mineral Exploitation sites should be tagged as service roads, unless they are noted by Tiger import as County Roads. Roads may be gated, use barrier=gate. On access roads on agricultural properties, they may also have need barrier=cattle_grid, use in conjunction with fence locations
See also Category:Highways.